Afforestation and bioenergy with carbon capture and storage (BECCS) are two typical land-based carbon dioxide removal strategies to combat climate change. We use life cycle assessment (LCA)-integrated Earth system modeling to compare their carbon sequestration efficiencies and associated environmental impacts. The results show that, for achieving the same 0.1 ℃ global cooling effect by year 2099 under a business-as-usual emission scenario, around 101 to 226 GtC (gigatonnes of carbon) need to be bio-assimilated on land via afforestation cumulatively, while BECCS demands 21.55 to 79.47 GtC to be extracted from vegetation carbon pool to produce bioelectricity. Our study confirms the relatively higher carbon dioxide removal potential of BECCS compared to afforestation and highlights the value of using the LCA-integrated Earth system modeling method to investigate the large-scale climate mitigation practices.